Montesquieu's tripartite system

The term is ascribed to French Enlightenment political philosopher Baron de Montesquieu. Montesquieu described division of political power among a legislature, an executive, and a judiciary. He based this model on the Constitution of the Roman Republic and the British constitutional system. Montesquieu took the view that the Roman Republic had powers separated so that no one could usurp complete power. In the British constitutional system, Montesquieu perceived a separation of powers among the monarch, Parliament, and the courts of law. Subsequent writers have noted that this was misleading, because the United Kingdom had a very closely connected legislature and executive, with further links to the judiciary (though combined with judicial independence).
Montesquieu did specify that "the independence of the judiciary has to be real, and not apparent merely". "The judiciary was generally seen as the most important of powers, independent and unchecked", and also considered it dangerous.
Power is frequently defined as the ability to influence the behavior of others with or without resistance. The term authority is often used for power perceived as legitimate by the social structure. Power can be seen as evil or unjust, but the exercise of power is accepted as endemic to humans as social beings. In the corporate environment, power is ften expressed as upward or downward. With downward power, a company's superior influences subordinates. When a company exerts upward power, it is the subordinates who influence the decisions of the leader (Greiner & Schein, 1988).
The use of power need not involve coercion (force or the threat of force). At one extreme, it more closely resembles what everyday English-speakers call influence, although some authors make a distinction between power and influence – the means by which power is used (Handy, C. 1993 Understanding Organisations).
Much of the recent sociological debate on power revolves around the issue of the enabling nature of power. A comprehensive account of power can be found in Steven Lukes Power: A Radical View where he discusses the three dimensions of power. Thus, power can be seen as various forms of constraint on human action, but also as that which makes action possible, although in a limited scope. Much of this debate is related to the works of the French philosopher Michel Foucault (1926–1984), who, following the Italian political philosopher Niccolo Machiavelli (1469–1527), sees power as "a complex strategic situation in a given society social setting". Being deeply structural, his concept involves both constraint and enablement. For a purely enabling (and voluntaristic) concept of power see the works of Anthony Giddens.